Two horses start trotting towards each other, one from A to B and another from B to A. They cross each other after one hour and the first horse reaches B, 5/6 hour before the second horse reaches A. If the distance between A and B is 50 km. what is the speed of the slower horse?

Correct Answer: 20 km\/h

If the speed of the faster horse be fs and that of slower horse be ss then

 fs+ss=501=50 

and       50ss-50fs=56

Now, you can go through options.

The speed of slower  horse is 20km/h

Since,   20+30=50

and  5020-5030=56